The present invention relates to an information retrieval technology, and in particular, to a technology suitably applicable to a job which, depending on a combination of retrieval conditions respectively established in an independent fashion for a plurality of columns constituting a record, extracts an objective record from a group of records.
As a so-called data base, there has been known a relational data base comprising a group of records in which the length of a plurality of columns constituting each record and the information arrange positions in the pertinent records are standardized or predetermined among the respective records of the group.
In this kind of the relational data base, as a method to extract an objective record depending on a combination of retrieval conditions independently applied to a plurality of columns constituting each record, there has been known a method described, for example, in the JP-A-58-139273 laid open on Aug. 18, 1983 (corresponding to U.S. Ser. No. 341,530 now U.S. Pat. No. 4,451,901 filed on Jan. 21, 1982).
The above-mentioned known method is summarized as follows: namely, in a case of a record extraction request depending on a combination of a plurality of retrieval conditions (queries), the system drives as many query processors as there are queries for the retrieval so as to accomplish the data retrieval processing.
However, the maximum number of retrieval conditions (queries) has heretofore been restricted by the number of the query processors, which leads to a problem that an increase of the retrieval conditions cannot be readily coped with.